Key operated switch for musical instruments



E m 8 E um 3 N em G. H. MARMONT ETAL KEY OPERATED SWITCH FOR MUSICAL INSTRUMENTS Filed Sept. 16, 1946 April 17, 1951 INVENTOR. GEORGE H. MARMONT BY MiR/QENA R/cE ATTORNEY MGEEQQ QOIWMQIK Patented Apr. 17, 1951 KEY OPERATED SWITCH FOR MUSICAL. I

INSTRUMENTS George H. Marmont, Chicago, Ill., and Warren A.

Rice, Detroit, Mich., assignors to Bendix Aviation Corporation, Detroit, Mich., a corporation of Delaware Application September 16, 1946, Serial No. 697,326

6 Claims.

This invention relates to musical instruments and more particularly to keys for an electronic piano.

Broadly the invention comprehends a key for an electronic piano characterized in that impact thereon is transmitted to a pivoted hammer,

which in turn transmits the impact to an actuator for a switch operative to close an electrical circuit for a period of time depending upon the strength of the impact. I

An object of this invention is to provide a key for an electronic piano in which the key action simulates that of the keys of a conventional piano.

Another object of the invention is to provide a key for an electronic piano and organ wherein the key action may be varied to simulate that of a piano or an organ.

Another object of the invention is to provide a key for a piano and organ operative in one phase to transmit impact on the key to an actuator for a switch so as to close the switch for a time interval dependent upon the force of the impact and in another phase to close a second switch for a time interval dependent upon the pressure applied to the key.

Other objects and advantages of the invention will appear from the following description when taken in connection with the drawings forming a part of this specification, and in which- Fig. l is a perspective view of a key partly broken away,

Fig. 2 is an enlarged fragmentary view of the key in side elevation, and

Fig. 3 is a diagrammatical illustration or a chart showing how contact depends on impact strength.

The key resembles that of a conventional piano and the key action is constructed to have a similar feel to that of a piano. However, the mechanism of the keys of the instrument, actuated by impact of the performers fingers upon the keys is different. Rather than causing a hammer to strike against a string, impact upon the key serves to momentarily close a switch. The length of time the switch is closed varies, approximately, from .0005 second to .01 second, the duration depending upon the strength of the impact.

Referring to the drawings for more specific details of the invention represents the base board of a piano. A support l2 suitably mounted on the base board has on one end a fulcrum I4 for a key l6, and on the other end of the support is a bracket consisting of an upright l8 having a web 20 received by a slot in the inner end of the key. The web extends above the upright and terminates in a forwardly projective portion 22 for the support of a leaf spring switch 24, the terminals of which are adapted to be connected by leads Z6 and 28. The switch serves to control the discharge of a condenser, and the condenser is discharged proportionately to the impact on the key.

An actuator 30 for the switch 24 is sleeved on and pivotally connected to the. extended portion 22 of the web 20. The actuator has on its free end a cam 32 for cooperation with the compliant member or the movable element of the switch and a felt pad 34, the purpose of which will heroine after appear. 4

A pin 36 threaded in the web 20 extends through an opening in the actuator and spring 38 sleeved on the pin between'the actuator and an adjustment nut 40 and covered as by a boot 42 serves to urge the actuator to its position of rest.

A hammer 44 has a bifurcated shank 46 straddling the web 20 and pivotally connected thereto as by a pintle, and the free end or head of the hammer has thereon a pad 48 normally resting on the key I6 and adapted to cooperatewith the pad 34 on the free end of the actuator 30 when the periormers fingers impinge upon the key.

A leaf spring switch 50 supported on the base [I] beneath the key l6 has spaced stationary contacts 52 and 54. The contact 52 is connected as by a lead 56 to a binding post, not shown, on the back of the support I8, and the binding post is adapted to be connected to the organ section of an electrical circuit fully shown and described in a copending application of George H. Marmont, Electronic Musical Instrument, filed Septemper 6, 1946, Ser. No. 697,324, now Patent 2,480,945 dated September 6, 1949. The contact 54 is connected as by a lead 58 to a binding post, also not shown, on the back of the support I 8 and this binding post is also adapted to be connected to the piano section of the electric circuit, and the compliant member or contactor 60 of the switch under control of the key is connected by a lead 62 to a binding post, also not shown, on the back of the support I8 and this binding post is connected in the electric circuit. Normally the contactor 60 is in engagement with the contact 54 and upon depression of the key the circuit is broken. When the instrument is played as an organ depression of the key results in engagement of the connector 60 with the contact 52 to close the circuit.

Upon striking the key 16 (actually a lever) the impact is transmitted to the pivoted hammer 44 and the hammer in turn transmits the impact to the actuator 30, the cam 32 of which engages the movable element of the switch 24 to close the circuit against the resistance of the spring 38. The actuator which possesses mass and the spring form a potentially oscillating system. However, the felt pads or dampers 34 and 48 cooperate with one another to inhibit the actuator from making more than one excursion, whereupon the actuator returns to its position of rest.

The compliant member or the movable element of the switch 24 rests against the cam 32 in such a way that, after the cam is moved through a short threshold distance, contact is made with the stationary member of the switch until the cam is almost returned to its rest position. It is, therefore, apparent, that although the period of excursion of the cam may be independent of impact, the fact that a threshold movement is required before the switch is closed means that the duration of contact of the switch depends upon the proportion of the cams total periodduring which the cam is moved beyond the threshold position.

A hypothetical plot of the cam excursion versus time for various impacts is shown in Fig. 3 and clearly illustrates the effect of the threshold.

The electrical circuit, hereinbefore referred to, translates the duration of the contact of the switch into a voltage amplitude supplied to the grid of the corresponding element of a tone tube.

While this invention has been described in connection with certain specific embodiments, the principle involved is susceptible of numerous other applications that will readily occur to persons skilled in the art.

Having thus described the various features of the invention, what we claim as new and desire to secure by Letter Patent is:

1. A key for a musical instrument comprising a movable member,a switch adapted to be actuated by depression of the member, a second switch, an actuator therefor, and a hammer cooperating with the actuator responsive to impact on the member to effectively close the second switch for an interval of time dependent upon the force of the impact.

2. A key for a musical instrument comprising a fulcrumed member, a switch adapted to be actuated by pressure imposed on the member, a second switch, an actuator therefor and a ham- 4 mer cooperating with the actuator and adapted to transmit energy from the member upon impaction thereof effective to close the second switch for an interval of time dependent upon the force of the impact.

3. A key for a musical instrument comprising a fulcrumed member, a switch controlled thereby, a second switch, an actuator therefor, and a hammer for transmitting energy from the fulcrumed member to the actuator so as to close the second switch fora time interval dependent upon the degree of impact on the fulcrumed member.

4. A key for a musical instrument comprising a fulcrum'ed member,a switch controlled thereby,

r a second switch, an actuator therefor, and a pivoted hammer for transmitting force from the fulcrumed member-to the actuator.

5. A key for a musical instrument comprising a fulcrumed member, a switch mounted beneath and controlled by the member, a second switch, an actuator therefor, means yieldingly resisting movement of the actuator, and a pivotally supported hammer responsive to impact of the fulcrumed member for the transmission of energy from the fulcrumed member to the actuator.

6. A key for a musical instrument comprisin a support, a bracket on one end of the support, a fulcrum on the other end of the support, a member supported on the fulcrumhaving a bifurcated end receiving the bracket, a switch mounted beneath and controlled by the member, a second switch supported on the bracket, an actuator therefor, means for imposing a load on the actuator and a hammer pivoted on the bracket for transmitting energy from the member on the fulcrum to the actuator.

GEORGE H. MARMONT. WARREN A. RICE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,521,793 Roe Jan. 6, 1925 1,745,265 Mecera Jan. 28, 1930 2,158,437 Shaw Ma 16, 1939 2,184,424 Hammond Dec. 26, 1939 2,271,460 Miessner Jan. 27, 1942 FOREIGN PATENTS Number Country Date 257,849 Great Britain Sept. 9, 1926 

